A wide variety of applications in science, industry and entertainment require high quality reproduction of sound using available sound recording techniques and equipment. High-quality, low-noise sound reproductions, for example, are of critical importance in the television and movie industry. There, crisp, clean voice and dialog reproduction must be achieved despite ambient and background noise levels of moderate to high amplitude.
One frequently encountered source of undesirable background noise is caused by air moving relative to the sound transducing device, which is most typically an omnidirectional or unidirectional microphone. As a result, a "whooshing" or rushing sound is imposed on the desired audio, thus resulting in deteriorated sound quality.
This type of noise may occur due to environmental or operational requirements and conditions. For example, wind noise often occurs when a microphone is panned during an indoor shoot, whether on a boom or simply held in hand with an extension. Likewise, such noise may be caused by forced air movement such as by fans or dynamic special effects equipment.
In certain applications, such as speeches or movie productions, unidirectional microphones are used which can reject most rear and lateral wind noise. However, this reduction is only effective at very low relative velocities, and will not reduce head-on wind noise. Further, unidirectional microphones are not suitable for all applications.
There are several prior art schemes that have been employed in an attempt to eliminate or reduce microphone wind noises. One is the use of a foam "sock" which is pulled over the microphone head. However, foam socks tend to physically deteriorate over time. As a result, foam particulates often fall into the microphone head, causing damage and reduced performance. Also, foam socks suffer the drawback of only being effective to reduce wind noise due to very slight breezes, up to approximately three miles per hour. This is a severe limitation in a broad spectrum of standard outdoor and indoor operating environments essential to the film and television industry. To overcome this limitation, electronic filtering techniques have been used to filter out wind noise resulting from velocities exceeding three miles per hour. Unfortunately, electronic filtering also attenuates desired audio frequencies, thereby substantially degrading sound quality.
Another prior art scheme used to reduce wind noise is the use of a gun-type microphone windshield. This device typically consists of suspending or supporting the microphone on a pair of suspension mounts, and enclosing the microphone in a plastic mesh cylinder lined with a wind interfering material. The suspension mounts, however, can obstruct the soundfield near the front of the microphone. Also, these units include a large air space between the interior surface of the windshield and the surface of the microphone. Thus, the diameter of the windshield is typically 3 to 5 times larger than the diameter of the microphone, and may intefere with a scene.
The prior art suspension mount wind shield also suffers the drawback of being bulky and cumbersome to handle. In addition, they are not suitable for direct mounting on home or professional video equipment which commonly include an integral microphone, because of their size and because they require an air gap which creates a large diameter apparatus.